Air/Fuel Ratios and Ambient Temps Ques.
 

I'm trying to get everything straightened out before I start into any tuning at all.... what kind of magnitude of changes will occur in the typical ambient temperature range (from about 0 to 100 degrees F) ? Or should I say, if I tune my car to about 11.2 A/F at 80 deg F how much change should I expect at 10 deg F (and when I'm not on the dyno with wideband to know!) I know I could get my texts out figure out density changes but obviously a lot more is invloved. Anyone know a rule of thumb? Thanks.

Alex

Alex,

I don't have any insight for you on your question. But keep in mind that the PFC adjusts IGN based on temp too.

Water temps above 110C result in IGN retard as with intake air over 80 (6 and 3 degrees, respectively for me.)

The PFC has correction factors for fuel delivery as a function of intake air temp and other variables. I don't believe these to be very well thought out, however, and it can result in lean conditions under the right circumstances. Unless you change your settings with the datalogit, NEVER run full boost in the winter under the following conditions: warm engine turned off and allowed to heat soak then engine started. The intake air temps will be high which leans out the car while the cold inlet air will be dense both contirbuting to lean condition.